Process of preparing nitro-



go The reaction proceeds in the following manner:

00 H OTNOZ converted into the nitrate in the manner described ing the corresponding nitro-hydroxypyridine or dine-nitrate are gradually introduced at 20 C.

nitric acid has a nitrating and oxidizing action 3, 13 grams of 3-hydroxy-4-methylpyridine, 100

- crystallize well; they decompose when heated. cooling, into 150 cc. of concentrated sulfuric acid, 110

Patented May 1, 1934 7 g I UNITED STATES PATENT- OFFICES PROCESS OF PREPARING NITRO-B- HYDROXY PYRIDINES Otto Wulff, Hofheim in Taunus, Germany, assignor to I. G. Farbenindustrie Aktiengesellschaft, Frankfort-on-the-Main, Germany I N0 Drawing. Application July 17, 1931, Serial No. 551,568. In Germany August 2, 1930 4 Claims. (01. 260-42) The present invention relates to the prepara- The nitro-o-hydroxy-pyridine compounds obtion of nitrates of p-hydroxypyridine and its tained from them are identical with the coralkyl derivatives and nitro-li-hydroxypyridine responding substances obtainable according to and its alkyl derivatives. process described in my co-pending U. S. appli- I have found that nitro-p-hydroxy compounds cation Serial No. 485,311, filed on September 29,

of the pyridine series can be obtained by first 1930. causing nitric acid to act upon a compound of The following examples serve to illustrate the the following formula: invention, but they are not intended to limit it X thereto:

l 1. 32 grams of B-hydroxypyridine are dissolved X in 200 cc. of a nitric acid of a specific gravity of 1.053 and the solution is evaporated on the water- X bath to a considerable extent. After cooling, the N colorless nitrate which has crystallized is filtered by suction and carefully dried. The yield amounts to 52 grams; melting point 133 C. with decomposition.

These 52 grams of 5-hydroxypyridine-nitrate are introduced at 50 C. into 300 cc. of concentrated sulfuric acid and the whole is further heated for a quarter of an hour at 50 C. The sulfuric acid may also be caused to run into the nitrate and the mixture then stirred, if necessary while heating, until the reaction is complete. After X cooling to room temperature, the reaction mixture is introduced into ice water, while stirring,

X 0H and worked up in the usual manner. 23 grams of nitro-c-hydroxypyridine (:50 per cent. of the X X theory) are obtained; melting point 68 C.-69 C.

N 2. 18 grams of 5-hydroxy2-methylpyridine are wherein X stands for hydrogen or at most three Xs stand for alkyl groups and then eliminating water from the nitrate thus obtained by the action of sulfuric acid.

When reacting with nitric acid upon o-hydroxypyridine or its alkyl derivatives there is first obtained the corresponding nitrate of the formula the Xs having the same meaning as in the above in Example 1. The yield amounts to 26 grams; formula, whereupon, under the influence of sulmelting point C.-126 C. with decomposifuric acid, the group NO2 substitutes one hydroti n,

- gen atom of the pyridine nucleus, thus form- These 26 grams of 5-hydroXy-2-methylpyri- 9O nitro-hydroxyalkylpyridine compound. The hyinto cc. of concentrated sulfuric acidjwhile drogen atom replaced y the nitro r up oomstirring. Stirring is continued for half an hour.

bines with the hy g atom and ygen atom The mixture is then introduced into ice water, attached to the nitrogen and is eliminated in the hil stirring during which operation th it form of water. 5-hydroxy-2-methylpyridine immediately sepa- T sy formation of nitrates of oyd xyrates in form of crystals. A further quantity can Pyridines and their Conversion into -fistill be obtained from the mother liquor. The hydroxy derivatives of the pyridine series are suryield amounts t 20 grams (:30 per t of t prising, because it is known that even aqueous theory); melting point 10"! C.108 C.

upo p e l or ot aromatic hydroXy-oomobtainable according to the process described in pounds. my co-pending U. S. application Serial No. 405,289, As a startin mat there y instance filed on November 6, 1929 are converted into the i be used 3 y y-p$f Y- 3 nitrate in the manner described in Example 1. 105

py d 3- Y yhy -5- thy1-py di The yield amounts to 24 grams; melting point 136 3-hydroXy-2.4.5-trimethyl-pyridine, 5 -hydroXy C. with decomposition. 2-propyl-pyridine, 5-hydr0Xy-2-butyl-pyridine. These 24 grams of 3-hydroxy-4-methylpyri- The nitrates are colorless substances which dine-nitrate are gradually introduced, while well the temperature being kept at 0-5 C. The mass is then introduced into ice water, while stirring, and worked up in the manner described in Example 2.

1'7 grams of nitro-3-hydroxy-4-methylpyridine (:74 per cent. of the theory) are obtained; melting point 90 C.-92 C.

4. 11.5 grams of 3-hydroxy-2-methyl-5-ethylpyridine (obtainable according to the process described in my co-pending U. S. application Serial No. 405,289, filed on November 6, 1929 are dissolved in cc. of a nitric acid of specific gravity of 1.053 and the solution is carefully evaporated, finally under reduced pressure and at a temperature below 60 C. The residue, which is at first a thick oil, constitutes the nitrate of the 3-hydroxy-2-methyl-5-ethyl-pyridine and can immediately be worked up. After standing for a long time, the nitrate crystallizes; it forms colorless crystals which are very easily soluble in water, melt at 76 C.78 C. and decompose at 95 C.- 100 C.

For converting the nitrate into the nitro-compound, the crude nitrate is introduced, while Well cooling, into '75 cc. of concentrated sulfuric acid at a temperature of 05 C. The product is worked up as described in Example 2.

6 grams of nitro-3-hydroxy-2-methyl-5-ethylwherein X stands for hydrogen or at most three Xs stand for alkyl groups and then causing sulfuric acid to act upon the nitrate thus obtained.

2. The process which comprises causing nitric acid to act upon p-hydroxypyridine and then causing sulfuric acid to act upon the nitrate thus obtained.

3. The process which comprises causing nitric acid to act upon 5-hydroxy-Z-methyl-pyridine and then causing sulfuric acid to act upon the nitrate thus obtained.

4. The process which comprises causing nitric acid to act upon 3-hydroxyi-methyl-pyridine and then causing sulfuric acid to act upon the nitrate thus obtained.

OTTO WULFF. 

